In manual conduction soldering, heat is conducted from the soldering tip to the soldering connection. That heat activates the flux, melts the soldering alloy so that it may wet the base metal and permits the distribution of the solder by capillary action.
The procedures selected to make the soldered joint should provide the proper soldering temperature, heat distribution, and ratio of heating and cooling commensurate with the properties of the base metal and requirements of the finished product. Therefore, it is apparent that a stable soldering temperature contributes to the reliability of a soldered assembly and permits the production of a properly soldered assembly to be readily repeated. However, thermal losses occur at the soldering tip as the heat is absorbed by the connection. More specifically, the soldering tip temperature decreases during the soldering operation in accordance with the mass and thermal characteristics of the tip and connection as well as the thermal power capability of the soldering iron.
Attempts to vary the heat delivered to the soldering tip in accordance with tip loading have included electronically controlled soldering tools having sensors disposed in a location remote from the soldering tip's working surface. Among the drawbacks of these systems is their slow response to actual tip loading due to the remote sensor location. A slow response time will preclude the control device from immediately turning the heater on after the tip is loaded resulting in excessive tip temperature drop. Furthermore, the slow response time will preclude the control device from immediately turning the heater off after the tip is unloaded resulting in excessive tip temperature overshoot. Another drawback of these systems is the inability of the remotely positioned sensor to measure the actual tip temperatures, i.e., the temperature of the tip's working surface, which results in the collection of inaccurate, and possibly inconsistent temperature data. Furthermore, these problems are exacerbated under conditions where the tip is placed under a relatively light load.
Accordingly, there is a need to provide a heating system that would rapidly respond to these thermal losses to maintain a more constant soldering temperature.
The operator also contributes to temperature drop in manual conduction soldering, for example, by controlling the travel speed of the soldering tip along the connection. Thus, it is important to control operator techniques so that the operator spends consistent amounts of time during the connection interval for similar assemblies. Previous attempts to monitor the manual soldering process and gather information associated with heat transfer at the soldering connection also have included placing temperature sensors in the vicinity of the connection, i.e., spaced from the working surface of the soldering tip. However, among the drawbacks of these systems include distinguishing the data associated with certain soldering operations that make-up a cycle, i.e., distinguishing the time the operator spends soldering, cleaning the tip to remove oxides and solder therefrom (sponge wipe) and transporting the tip to a connection. It is particularly difficult to distinguish the data associated with the sponge wipe(s) from that associated with the soldering operation. This is due to the fact that the soldering tip temperature profile decays during both the sponge wipe and soldering operations. Thus, there is a need to develop a system that can collect tip temperature data and present the temperature-time profile therefor in a manner such that the data associated with each soldering operation can be readily distinguished.